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      <a href="/2016/07/22/angular-note-7-load-image/" title="Angular使用笔记7--使用File API编写预览图片的指令" itemprop="url">Angular使用笔记7--使用File API编写预览图片的指令</a>
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      <a href="https://godbasin.github.io" title="被删">被删</a>
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    <time datetime="2016-07-22T13:53:23.000Z" itemprop="datePublished">2016-07-22</time>
    更新日期:<time datetime="2018-12-18T15:28:34.227Z" itemprop="dateModified">2018-12-18</time>
    
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			<strong class="toc-title">文章目录</strong>
		<ol class="toc"><li class="toc-item toc-level-2"><a class="toc-link" href="#File-API"><span class="toc-number">1.</span> <span class="toc-text">File API</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#有关File-API"><span class="toc-number">1.1.</span> <span class="toc-text">有关File API</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#检查File-API兼容性"><span class="toc-number">1.2.</span> <span class="toc-text">检查File API兼容性</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#参考"><span class="toc-number">1.3.</span> <span class="toc-text">参考</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#FileList接口"><span class="toc-number">1.4.</span> <span class="toc-text">FileList接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#Blob接口"><span class="toc-number">1.5.</span> <span class="toc-text">Blob接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#File接口"><span class="toc-number">1.6.</span> <span class="toc-text">File接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#FileReader"><span class="toc-number">1.7.</span> <span class="toc-text">FileReader</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#编写预览图片的指令"><span class="toc-number">2.</span> <span class="toc-text">编写预览图片的指令</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#添加模板"><span class="toc-number">2.1.</span> <span class="toc-text">添加模板</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#设置作用域"><span class="toc-number">2.2.</span> <span class="toc-text">设置作用域</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#设置link函数"><span class="toc-number">2.3.</span> <span class="toc-text">设置link函数</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#使用预览图片的指令"><span class="toc-number">3.</span> <span class="toc-text">使用预览图片的指令</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#在index页面中添加指令"><span class="toc-number">3.1.</span> <span class="toc-text">在index页面中添加指令</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#在IndexCtrl控制器中添加loadphoto函数逻辑"><span class="toc-number">3.2.</span> <span class="toc-text">在IndexCtrl控制器中添加loadphoto函数逻辑</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#最终效果"><span class="toc-number">3.3.</span> <span class="toc-text">最终效果</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#结束语"><span class="toc-number">4.</span> <span class="toc-text">结束语</span></a></li></ol>
		</div>
		
		<p>最近的一个项目使用AngularJS(v1.2.6)作为前端的框架，《Angular使用笔记》系列用于记录过程中的一些使用和解决方法。<br>本文记录使用File API编写预览图片的指令的过程。<br><a id="more"></a></p>
<h2 id="File-API"><a href="#File-API" class="headerlink" title="File API"></a>File API</h2><hr>
<p>上一节我们已经稍微介绍了一下。</p>
<h3 id="有关File-API"><a href="#有关File-API" class="headerlink" title="有关File API"></a>有关File API</h3><ul>
<li>File接口提供了文件的信息，以及文件内容的存取方法</li>
<li>对象可以用来获取某个文件的信息,还可以用来读取这个文件的内容</li>
<li>通常情况下,File对象是来自用户在一个<code>&lt;input&gt;</code>元素上选择文件后返回的FileList对象,也可以是来自由拖放操作生成的 DataTransfer对象</li>
</ul>
<h3 id="检查File-API兼容性"><a href="#检查File-API兼容性" class="headerlink" title="检查File API兼容性"></a>检查File API兼容性</h3><ul>
<li>window.File&amp;&amp;window.FileReader&amp;&amp;window.FileList&amp;&amp;window.Blob</li>
</ul>
<h3 id="参考"><a href="#参考" class="headerlink" title="参考"></a>参考</h3><ul>
<li><a href="http://bulaoge.net/topic.blg?dmn=g3g4&amp;tid=2344378#Content" target="_blank" rel="external">《HTML 5中的文件处理之FileAPI》</a></li>
<li>以下内容主要来自该文章</li>
</ul>
<h3 id="FileList接口"><a href="#FileList接口" class="headerlink" title="FileList接口"></a>FileList接口</h3><p>可以用来代表一组文件的JS对象，比如用户通过<code>input[type=&quot;file&quot;]</code>元素选中的本地文件列表<br><figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div></pre></td><td class="code"><pre><div class="line">#FileList[index] // 得到第index个文件</div></pre></td></tr></table></figure></p>
<h3 id="Blob接口"><a href="#Blob接口" class="headerlink" title="Blob接口"></a>Blob接口</h3><p>用来代表一段二进制数据，并且允许我们通过JS对其数据以字节为单位进行“切割”<br><figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div></pre></td><td class="code"><pre><div class="line">#Blob.size // 只读特性，数据的字节数  </div><div class="line">#Blob.slice(start, length) // 将当前文件切割并将结果返回</div></pre></td></tr></table></figure></p>
<h3 id="File接口"><a href="#File接口" class="headerlink" title="File接口"></a>File接口</h3><p>用来代步一个文件，是从Blob接口继承而来的，并在此基础上增加了诸如文件名、MIME类型之类的特性<br><figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div></pre></td><td class="code"><pre><div class="line">#File.size // 继承自Blob，意义同上  </div><div class="line">#File.slice(start, length) // 继承自Blob，意义同上  </div><div class="line">#File.name // 只读属性，文件名  </div><div class="line">#File.type // 只读属性，文件的MIME类型  </div><div class="line">#File.urn // 只读属性，代表该文件的URN，几乎用不到，暂且无视</div></pre></td></tr></table></figure></p>
<h3 id="FileReader"><a href="#FileReader" class="headerlink" title="FileReader"></a>FileReader</h3><p>提供读取文件的方法和事件，大多数情况下我们主要使用FileReader。</p>
<ul>
<li>FileReader方法</li>
</ul>
<figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div></pre></td><td class="code"><pre><div class="line">#FileReader.readAsBinaryString(blob/file) // 以二进制格式读取文件内容  </div><div class="line">#FileReader.readAsText(file, [encoding]) // 以文本(及字符串)格式读取文件内容，并且可以强制选择文件编码  </div><div class="line">#FileReader.readAsDataURL(file) // 以DataURL格式读取文件内容  </div><div class="line">#FileReader.abort() // 终止读取操作</div></pre></td></tr></table></figure>
<ul>
<li>FileReader事件</li>
</ul>
<figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div></pre></td><td class="code"><pre><div class="line">#FileReader.onloadstart // 读取操作开始时触发  </div><div class="line">#FileReader.onload // 读取操作成功时触发  </div><div class="line">#FileReader.onloadend // 读取操作完成时触发(不论成功还是失败)  </div><div class="line">#FileReader.onprogress // 读取操作过程中触发  </div><div class="line">#FileReader.onabort // 读取操作被中断时触发  </div><div class="line">#FileReader.onerror // 读取操作失败时触发</div></pre></td></tr></table></figure>
<ul>
<li>FileReader属性</li>
</ul>
<figure class="highlight"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div></pre></td><td class="code"><pre><div class="line">#FileReader.result // 读取的结果(二进制、文本或DataURL格式)  </div><div class="line">#FileReader.readyState // 读取操作的状态(EMPTY、LOADING、DONE)</div></pre></td></tr></table></figure>
<h2 id="编写预览图片的指令"><a href="#编写预览图片的指令" class="headerlink" title="编写预览图片的指令"></a>编写预览图片的指令</h2><hr>
<p>我们知道，在AngularJS中不推荐在控制器中添加DOM操作，所以我们将要把DOM封装到指令里面。<br>在directives文件夹里添加otherDir.js文件，并在index启动页面中引入。</p>
<h3 id="添加模板"><a href="#添加模板" class="headerlink" title="添加模板"></a>添加模板</h3><p>模板很简单，也就是一个按钮。</p>
<ul>
<li>按钮的字可以自定义，这里使用了text变量</li>
<li>该按钮里面需要将file input隐藏，故使用了样式input{display: none;}</li>
<li>该按钮绑定了click事件，来触发选择图片的动作</li>
</ul>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div></pre></td><td class="code"><pre><div class="line">template: <span class="string">'&lt;div class="file-input" ng-click="click()"&gt;'</span> +</div><div class="line">  <span class="string">'&lt;a class="btn btn-default"&gt;&#123;&#123; text &#125;&#125;&lt;/a&gt;'</span> +</div><div class="line">  <span class="string">'&lt;/div&gt;'</span>,</div></pre></td></tr></table></figure>
<h3 id="设置作用域"><a href="#设置作用域" class="headerlink" title="设置作用域"></a>设置作用域</h3><p>指令设置单独作用域，传入两个参数：</p>
<ul>
<li>text: 使用@进行单向绑定，设置按钮显示的值</li>
<li>loadphoto： 使用=进行双向绑定，传入函数用于获取返回的图片url</li>
</ul>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div></pre></td><td class="code"><pre><div class="line">scope: &#123;</div><div class="line">  <span class="attr">loadphoto</span>: <span class="string">"=loadphoto"</span>,</div><div class="line">  <span class="attr">text</span>: <span class="string">"@text"</span>,</div><div class="line">&#125;,</div></pre></td></tr></table></figure>
<p>有关作用域可以参照<a href="/2016/07/16/angular-note-5-fullfill-index/">《Angular使用笔记5–作用域简单分析以及制作index页面》</a></p>
<h3 id="设置link函数"><a href="#设置link函数" class="headerlink" title="设置link函数"></a>设置link函数</h3><p>link函数里面主要为绑定click事件的处理。<br>主要逻辑：</p>
<ul>
<li>从该指令根节点元素element中查找file input</li>
<li>如果不存在则创建新的file input，如果已经存在则先移除再创建（使得可后续触发点击和change事件）</li>
<li>给input绑定change事件，选中图片之后触发加载FileReader读取图片地址</li>
<li>通过函数loadphoto返回图片地址</li>
<li>设置好上述事件之后，即刻触发点击</li>
</ul>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div><div class="line">11</div><div class="line">12</div><div class="line">13</div><div class="line">14</div><div class="line">15</div><div class="line">16</div><div class="line">17</div><div class="line">18</div><div class="line">19</div><div class="line">20</div><div class="line">21</div><div class="line">22</div><div class="line">23</div><div class="line">24</div><div class="line">25</div><div class="line">26</div><div class="line">27</div><div class="line">28</div><div class="line">29</div><div class="line">30</div><div class="line">31</div><div class="line">32</div><div class="line">33</div><div class="line">34</div><div class="line">35</div><div class="line">36</div></pre></td><td class="code"><pre><div class="line">link: <span class="function"><span class="keyword">function</span>(<span class="params">scope, element, attrs</span>) </span>&#123;</div><div class="line">  scope.click = <span class="function"><span class="keyword">function</span>(<span class="params"></span>) </span>&#123;</div><div class="line">    <span class="comment">//从该指令根节点元素element中查找input</span></div><div class="line">    <span class="keyword">var</span> $input = element[<span class="number">0</span>].getElementsByTagName(<span class="string">"input"</span>);</div><div class="line">    <span class="comment">//如果已经存在则先移除input</span></div><div class="line">    <span class="keyword">if</span> ($input.length) &#123;</div><div class="line">      element[<span class="number">0</span>].removeChild($input[<span class="number">0</span>]);</div><div class="line">    &#125;</div><div class="line">    <span class="comment">//创建新的file input</span></div><div class="line">    $input = <span class="built_in">document</span>.createElement(<span class="string">"input"</span>);</div><div class="line">    $input.setAttribute(<span class="string">"type"</span>, <span class="string">"file"</span>);</div><div class="line">    $input.setAttribute(<span class="string">"name"</span>, <span class="string">"file"</span>);</div><div class="line">    $input.setAttribute(<span class="string">"accept"</span>, <span class="string">"image/*"</span>);</div><div class="line">    <span class="comment">//将input添加进该指令根节点元素element中</span></div><div class="line">    element[<span class="number">0</span>].appendChild($input);</div><div class="line">    <span class="comment">//绑定click事件，取消事件的传播</span></div><div class="line">    $input.addEventListener(<span class="string">"click"</span>, <span class="function"><span class="keyword">function</span>(<span class="params"></span>) </span>&#123;</div><div class="line">      event.stopPropagation();</div><div class="line">    &#125;);</div><div class="line">    <span class="comment">//绑定change事件，分析获取图片url</span></div><div class="line">    $input.addEventListener(<span class="string">"change"</span>, <span class="function"><span class="keyword">function</span>(<span class="params">e</span>) </span>&#123;</div><div class="line">      <span class="keyword">var</span> fReader = <span class="keyword">new</span> FileReader(),</div><div class="line">        file = e.target.files[<span class="number">0</span>];</div><div class="line">      fReader.readAsDataURL(file); <span class="comment">//获取图片url</span></div><div class="line">      fReader.onload = <span class="function"><span class="keyword">function</span>(<span class="params">e</span>) </span>&#123;</div><div class="line">        <span class="keyword">var</span> url = e.target.result;</div><div class="line">        scope.loadphoto(url); <span class="comment">//返回图片url</span></div><div class="line">      &#125;;</div><div class="line">    &#125;, <span class="literal">false</span>);</div><div class="line">    <span class="comment">//即刻触发点击</span></div><div class="line">    $timeout(<span class="function"><span class="keyword">function</span>(<span class="params"></span>) </span>&#123;</div><div class="line">      $input.click();</div><div class="line">    &#125;);</div><div class="line"></div><div class="line">  &#125;;</div><div class="line">&#125;,</div></pre></td></tr></table></figure>
<h2 id="使用预览图片的指令"><a href="#使用预览图片的指令" class="headerlink" title="使用预览图片的指令"></a>使用预览图片的指令</h2><hr>
<h3 id="在index页面中添加指令"><a href="#在index页面中添加指令" class="headerlink" title="在index页面中添加指令"></a>在index页面中添加指令</h3><ul>
<li>在该页面设置头像对应模块添加该指令</li>
<li>传入text参数以及loadphoto函数</li>
<li>添加img用于展示图片，该img绑定ng-src，参数为avatar</li>
</ul>
<figure class="highlight html"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div></pre></td><td class="code"><pre><div class="line"><span class="tag">&lt;<span class="name">a</span> <span class="attr">file-input</span> <span class="attr">text</span>=<span class="string">"上传头像"</span> <span class="attr">loadphoto</span>=<span class="string">"loadphoto"</span>&gt;</span><span class="tag">&lt;/<span class="name">a</span>&gt;</span></div><div class="line"><span class="tag">&lt;<span class="name">img</span> <span class="attr">ng-src</span>=<span class="string">"&#123;&#123; avatar &#125;&#125;"</span>  /&gt;</span></div></pre></td></tr></table></figure>
<h3 id="在IndexCtrl控制器中添加loadphoto函数逻辑"><a href="#在IndexCtrl控制器中添加loadphoto函数逻辑" class="headerlink" title="在IndexCtrl控制器中添加loadphoto函数逻辑"></a>在IndexCtrl控制器中添加loadphoto函数逻辑</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div></pre></td><td class="code"><pre><div class="line">$scope.loadphoto = <span class="function"><span class="keyword">function</span>(<span class="params">url</span>)</span>&#123;</div><div class="line">  $scope.avatar = url; <span class="comment">//将avatar变量设置为url</span></div><div class="line">&#125;</div></pre></td></tr></table></figure>
<h3 id="最终效果"><a href="#最终效果" class="headerlink" title="最终效果"></a>最终效果</h3><p>如图：<br><img src="https://github-imglib-1255459943.cos.ap-chengdu.myqcloud.com/DC13.tmp.png" alt="image"></p>
<h2 id="结束语"><a href="#结束语" class="headerlink" title="结束语"></a>结束语</h2><hr>
<p>用file API实现图片预览已经成为一种流行方式了，可能如今对兼容性要求也没有很高的，当然对自己要求高的小伙伴们可以把兼容也做了，哈哈。<br><a href="https://github.com/godbasin/godbasin.github.io/tree/blog-codes/angular-notes/7-load-image" target="_blank" rel="external">此处查看项目代码（仅包含app部分）</a><br><a href="http://angular-notes.godbasin.com/7-load-image/index.html#/index" target="_blank" rel="external">此处查看页面效果</a></p>
  
		
		<p style="margin-top:50px;">
			查看Github有更多内容噢：<a href="https://github.com/godbasin">https://github.com/godbasin</a>
			<br>
			更欢迎来<a href="https://godbasin.github.io/front-end-playground">被删的前端游乐场</a>边撸猫边学前端噢
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	<img src="https://github-imglib-1255459943.cos.ap-chengdu.myqcloud.com/2code2.jpg" width="200" height="200" style="display:block;margin: 0 auto;" />
	<p style="text-align: center;margin-top: 10px;margin-bottom: 20px;">码生艰难，写文不易，给我家猪囤点猫粮了喵~</p>
	<div class="author-right">
  		<p>作者：被删</p>
  		<p>出处：<a href="https://godbasin.github.io">https://godbasin.github.io</a></p>
  		<p>本文版权归作者所有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。</p>
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  <strong class="toc-title">文章目录</strong>
  <ol class="toc"><li class="toc-item toc-level-2"><a class="toc-link" href="#File-API"><span class="toc-number">1.</span> <span class="toc-text">File API</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#有关File-API"><span class="toc-number">1.1.</span> <span class="toc-text">有关File API</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#检查File-API兼容性"><span class="toc-number">1.2.</span> <span class="toc-text">检查File API兼容性</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#参考"><span class="toc-number">1.3.</span> <span class="toc-text">参考</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#FileList接口"><span class="toc-number">1.4.</span> <span class="toc-text">FileList接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#Blob接口"><span class="toc-number">1.5.</span> <span class="toc-text">Blob接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#File接口"><span class="toc-number">1.6.</span> <span class="toc-text">File接口</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#FileReader"><span class="toc-number">1.7.</span> <span class="toc-text">FileReader</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#编写预览图片的指令"><span class="toc-number">2.</span> <span class="toc-text">编写预览图片的指令</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#添加模板"><span class="toc-number">2.1.</span> <span class="toc-text">添加模板</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#设置作用域"><span class="toc-number">2.2.</span> <span class="toc-text">设置作用域</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#设置link函数"><span class="toc-number">2.3.</span> <span class="toc-text">设置link函数</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#使用预览图片的指令"><span class="toc-number">3.</span> <span class="toc-text">使用预览图片的指令</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#在index页面中添加指令"><span class="toc-number">3.1.</span> <span class="toc-text">在index页面中添加指令</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#在IndexCtrl控制器中添加loadphoto函数逻辑"><span class="toc-number">3.2.</span> <span class="toc-text">在IndexCtrl控制器中添加loadphoto函数逻辑</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#最终效果"><span class="toc-number">3.3.</span> <span class="toc-text">最终效果</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#结束语"><span class="toc-number">4.</span> <span class="toc-text">结束语</span></a></li></ol>
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